1. Field of the Invention
The present invention relates to a dispersion of an amorphous urethanized unsaturated polyester resin based on particular dicidol isomers and acids.
2. Discussion of the Background
Unsaturated polyester resins (UP resins) are known. They are prepared by condensing saturated and unsaturated dicarboxylic acids or their anhydrides with diols. Their properties depend largely on the nature and proportion of the starting materials.
As carriers of the polymerizable double bonds it is usual to use α,β-unsaturated acids, primarily maleic acid or its anhydride or fumaric acid; unsaturated diols are of minor importance. The higher the double bond content, i.e., the shorter the distance between the double bonds in the chain molecules, the more reactive the polyester resin. It polymerizes very rapidly, evolving large quantities of heat and undergoing a high level of volume contraction, to form a highly crosslinked and therefore relatively brittle end product. Consequently the reactive double bonds in the polyester molecule are “diluted” by cocondensing saturated aliphatic or aromatic dicarboxylic acids. Straight-chain and branched diols are used as alcohol components. The individual UP resin types differ not only in the components used to prepare them but also in the proportion of saturated to unsaturated acids, which determines the degree of crosslinking in the polymerization, the degree of condensation, i.e., the molar mass, the acid number and OH number, i.e., the nature of the end groups in the chain molecules, the monomer content, and the nature of the additions (Ullmann's Encyclopedia of Industrial Chemistry, Vol. A21, p. 217 ff, 1992).
UP resins based on dicidol as the diol component are known from, for example, DE 924 889, DE 953 117, DE 22 45 110, DE 27 21 989, EP 0 114 208, and EP 0 934 988.